These examples reflect some of the 77 discrete disorders of sleep catalogued in the new edition of the International Classification of Sleep Disorders (ICSD-Revised) (Rochester, Minn: American Sleep Disorders Association; 1997).

The first case illustrates rapid eye movement behavior disorder, often associated with neurologic illnesses. The second depicts the sleep phase delay syndrome, not a disorder of sleep per se but rather of the timing of sleep. The adolescent may have narcolepsy. He may be using illicit drugs. Or he just may not be getting enough sleep.